Li Cong, Zhao Tianlun, Yu Hurong, Li Cheng, Deng Xiaolei, Dong Yating, Zhang Fan, Zhang Yi, Mei Lei, Chen Jinhong, Zhu Shuijin
Department of Agronomy, Zhejiang University, Zhejiang, 310058, Hangzhou, China.
BMC Genomics. 2018 Dec 12;19(1):910. doi: 10.1186/s12864-018-5289-2.
Quantitative trait loci (QTL) mapping provides a powerful tool to unravel the genetic bases of cotton yield and its components, as well as their heterosis. In the present study, the genetic basis underlying inbreeding depression and heterosis for yield and yield components of upland cotton was investigated in recombinant inbred line (RIL), immortalized F (IF), and two backcross (BCF) populations based on a high-density SNP linkage map across four environments.
Significant inbreeding depression of fruit branches per plant (FB), boll numbers per plant (BN), seed cotton yield (SY), and lint yield (LY) in RIL population and high levels of heterosis for SY, LY, and boll weight (BW) in IF and two BCF populations were observed. A total of 285 QTLs were identified in the four related populations using a composite interval mapping approach. In the IF population, 26.60% partially dominant (PD) QTLs and 71.28% over-dominant (OD) QTLs were identified. In two BCF populations, 42.41% additive QTLs, 4.19% PD QTLs, and 53.40% OD QTLs were detected. For multi-environment analysis, phenotypic variances (PV) explained by e-QTLs were higher than those by m-QTLs in each of the populations, and the average PV of m-QTLs and e-QTLs explained by QTL × environment interactions occupied a considerable proportion of total PV in all seven datasets.
At the single-locus level, the genetic bases of heterosis varied in different populations. Partial dominance and over-dominance were the main cause of heterosis in the IF population, while additive effects and over-dominance were the main genetic bases of heterosis in two BCF populations. In addition, the various genetic components to heterosis presented trait specificity. In the multi-environment model analysis, epistasis was a common feature of most loci associated with inbreeding depression and heterosis. Furthermore, the environment was a critical factor in the expression of these m-QTLs and e-QTLs. Altogether, additive effects, over-dominance, epistasis and environmental interactions all contributed to the heterosis of yield and its components in upland cotton, with over-dominance and epistasis more important than the others.
数量性状基因座(QTL)定位为揭示棉花产量及其构成因素的遗传基础以及杂种优势提供了强大工具。在本研究中,基于跨越四个环境的高密度单核苷酸多态性(SNP)连锁图谱,在重组自交系(RIL)、永久F2(IF)和两个回交(BCF)群体中研究了陆地棉产量及其构成因素的近交衰退和杂种优势的遗传基础。
在RIL群体中观察到单株果枝数(FB)、单株铃数(BN)、籽棉产量(SY)和皮棉产量(LY)存在显著的近交衰退,在IF和两个BCF群体中观察到SY、LY和铃重(BW)具有较高水平的杂种优势。使用复合区间作图方法在四个相关群体中总共鉴定出285个QTL。在IF群体中,鉴定出26.60%的部分显性(PD)QTL和71.28%的超显性(OD)QTL。在两个BCF群体中,检测到42.41%的加性QTL、4.19%的PD QTL和53.40%的OD QTL。对于多环境分析,在每个群体中,由环境特异性QTL(e-QTL)解释的表型方差(PV)高于由多环境QTL(m-QTL)解释的表型方差,并且在所有七个数据集中,由QTL×环境互作解释的m-QTL和e-QTL的平均PV占总PV的相当大比例。
在单基因座水平上,杂种优势的遗传基础在不同群体中有所不同。部分显性和超显性是IF群体中杂种优势的主要原因,而加性效应和超显性是两个BCF群体中杂种优势的主要遗传基础。此外,杂种优势的各种遗传成分表现出性状特异性。在多环境模型分析中,上位性是大多数与近交衰退和杂种优势相关基因座的共同特征。此外,环境是这些m-QTL和e-QTL表达的关键因素。总之,加性效应、超显性、上位性和环境互作都对陆地棉产量及其构成因素的杂种优势有贡献,其中超显性和上位性比其他因素更重要。